You are answering a USMLE-style medical question. Question: A 55-year-old man presents into the emergency department with a severe cough and difficulty breathing. He says that he finds himself out of breath after taking a few steps, and has to sit down and rest, in order to continue. He also says that, at night, he has the greatest difficulty in breathing and usually uses at least 3 pillows to sleep comfortably. He mentions a cough that appears only at night, but which is persistent enough to wake him up from sleep. He mentions that he has had a ‘heart attack’ 5 years ago. He also says that he continues to consume alcohol on a regular basis even though his doctor has advised against it. He has brought his lab reports which he had recently got done on the suggestions of his family doctor. An electrocardiogram (ECG) and a chest X-ray are found. Which of the following is the next step in this patient’s management? Options: A) Computed Tomography (CT) B) Echocardiogram C) Stress test D) Cardiac biopsy Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.